ASNT Industrial Radiography Radiation Safety Practice Test

How do Van de Graaff generators obtain their electrons?

1. Through thermal emission

2. By electrostatic induction

3. By the electrostatic principle

4. Through magnetic confinement

The correct answer is: By the electrostatic principle

The correct understanding involves how Van de Graaff generators function, specifically focusing on the process of charge accumulation. Van de Graaff generators obtain their electrons primarily by the principle of electrostatic induction. In essence, a Van de Graaff generator operates by using a moving belt to transfer charge from one location to another. When the belt moves, it typically contacts a comb or a similar apparatus that allows for the transfer of electrons from a conductive material to the belt. As the belt continues to move upwards, it carries this charge to the top of the generator where it creates a high voltage. Electrostatic induction is crucial because it leads to the separation of charges; the influence of the moving charged belt induces an opposite charge on parts of the generator, leading to the accumulation of electrons without direct contact from a source of electrons. This process enables the generator to create high potentials for various applications, particularly in particle accelerators and other fields requiring high voltages. Understanding this process highlights the mechanism by which the Van de Graaff generator effectively harnesses and utilizes static electricity for its operations.